Sabots



July 21, 1964 E. c. ROEHRDANZ 3,141,412

SABOTS Filed May 18, 1961 Q INVENTOR [/rog C Roe/vraanz ATTORNEY 3,141,412 SABQTS Eiroy t3. Roehrdanz, 108 San Jose Ave., San Francisco, Calif. Filed May 18, 1961, Ser. No. 111,038 4 Ciaims. (Cl. 10293) This invention relates to an improvement in sabots and deals particularly with a plastic carrier designed to accommodate a projectile which is of substantially smaller diameter than the bore diameter of the rifle barrel from which the projectile is fired.

For many years experimental sabots have been produced which are designed to accommodate a projectile which is of smaller diameter than the bore of the rifle from which the projectile is fired. As the bore diameter of a rifle is increased, the size and powder capacity of the cartridge which can be used is also increased, and as a result, the muzzle velocity of a given weight projectile can be increased over that of a smaller diameter projectile of same weight. At the same time, however, an increase in the diameter of the projectile creates a greater resistance to the travel of the projectile through the air and as a result the projectile loses velocity and accuracy rather quickly. Through the use of a sabot which encircles the body of a projectile during the travel of the projectile through the rifle barrel, a projectile of approximately the same Weight as the larger diameter projectile may be employed. The smaller diameter projectile is better proportioned from an aerodynamic standpoint and accordingly, once it is fired from the barrel at the same velocity as the larger diameter projectile, it loses speed less rapidly and maintains a flatter trajectory and higher degree of accuracy at extended range. Obviously, the sabot must be designed to separate freely from the projectile as soon as the projectile leaves the rifle barrel.

For example, the cross section area of a .308 diameter bullet is 1.61 times greater than that of a .243 diameter bullet. Hence if two rifles are designed to operate at 50,000 pounds/in. pressure the .308 rifle will generate 1.61 times as much force on a bullet as will a .243 rifle. Force equals pressure times cross section area. Hence, Weight for weight a .308 diameter bullet can be given considerably more velocity than a .243 diameter bullet. There are super magnum rifles that occasionally blow up trying to get 3,400 ft./second with a 100 grain .243 bullet, but there are magnum rifles that can get up to 4,000 ft./ second with a 110 grain .308 diameter bullet.

In the past, numerous types of sabots have been produced, but have ben limited to laboratory use because of cost and inaccuracy. Most such sabots comprise a metal sleeve having a closed end which abuts the rear of the projectile, the sleeve being longitudinally split or otherwise formed so that it will fall free of the projectile as soon as it leaves the confinement of the rifle barrel. Such sabots are usually relatively expensive, and must be formed with considerable accuracy, as the sabot must be rotated about its axis by the rifling in the rifle barrel, and at the same time must impart the rotation to the projectile. It is an object of the present invention to provide a sabot which may be made at a relatively low cost, and yet which will have advantages superior to that of the structures previously employed.

An object of the present invention resides in the provision of sabot which is formed of plastic which therefore may be produced in quantity at a relatively low price. Sabots of this type may be accurately molded or machined to a predetermined size, and if a proper type of plastic is employed, will function as effectively and more accurately than the metal sabots which have been previcusly produced.

3,14L4E2 Patented July 21, T1964 A feature of the present invention resides in the provision of a sabot which may be formed in one piece, thereby greatly facilitating the assembly of the projectile into the cartridge case. The sabot is so formed as to be self splitting to insure its separation from the projectile upon leaving the rifle barrel, thereby permitting the projectile to travel through the air with high speed and remarkable accuracy.

The self-splitting feature of the present invention, and the manner in which it is obtained, resides in the provision of a sabot which is formed with a cavity between the closed end of the sabot and the rear end of the projectile. As the cartridge is fired, the terrific force of the exploding gases tends to collapse the cavity, producing stresses in the closed rear end of the sabot which continue into the walls of the sabot encircling the projectile. These stresses produce cracks from end to end of the sabot which do not interfere with the function of the sabot during its travel through the rifle barrel. However, as soon as the projectile emerges from the muzzle of the rifle, the cracks and the centrifugal force on the walls of the sabot cause the sabot to freely separate and fall apart, and therefore do not interfere with the speed or accuracy of the projectile.

In the interests of practicality, the plastic sabots have been designed to use commercially available bullets. In the case of the larger diameter bullets it may be necessary that several small grooves be cut longitudinally into the body of the bullet in order to prevent any spin slippage between the bullet and the plastic sabot when the sabot is rotated by the gun barrel rifiing. But in the case of smaller diameter bullets, .243, these grooves have not appeared to be necessary.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification:

FIGURE 1 is an elevational view of a rifle cartridge with the sabot in place therein.

FIGURE 2 is a perspective view of the empty sabot before use.

FIGURE 3 is a longitudinal sectional view through the sabot shown in FIGURE 2.

FIGURE 4 is a sectional view showing the projectile mounted within the sabot.

FIGURE 5 is a side elevational view of the projectile and sabot showing the manner in which the sabot is longitudinally split as the cartridge is exploded.

FIGURE 6 is a longitudinal sectional view through a modified form of sabot.

As is indicated in FIGURE 1 of the drawings, the sabot A is used in conjunction with a cartridge such as B. While the sabots have been mainly used in rifles having a bore or inner barrel diameter in the neighborhood or A to of an inch, the particular size may be varied considerably, and the sizes which have been, and will be mentioned, are only for the purpose of illustration.

In the preferred form, the sabot A includes a generally cylindrical sleeve 10 having a closed end 11. The outside diameter of the sleeve 10 is preferably slightly greater than the outside diameter of the projectile which would usually be used in the same rifle. The inside diameter 12 of the sleeve 10 is usually slightly smaller than the outside diameter of the projectile C which is used in conjunction therewith so that the projectile fits snugly within the sleeve and usually expands it slightly.

As a typical example, but not by way of limitation, the sabot and projectile used in a 30-06 rifle may have an outside diameter of .3100 to .3110 inch. The inner diameter 12 may measure A of an inch and may be designed to fit a projectile C having an outer diameter of .257 inch.

The sabot A is shown as having an end surface 13 which is on a plane normal to the axis of the sabot. However, the inner surface of the end Wall 11 is provided with a conical surface 14 which is spaced from the lower ends 15 of the projectile C except at its outer periphery. \Vhile the cone shaped recess has been found very desirable, and to function with great effectiveness, the specific shape of the cavity may be varied.

As will be indicated in FIGURE 4 of the drawings, the shape of the inner wall of the projectile cavity forms an air space or pocket between the sabot end wall 11 and the projectile end wall 15. The sabot is machined of a plastic such as that commercially known as Polypenco Nylon 101 or an equivalent. If the plastic is too flexible and pliable, it will not crack or function as effectively as a somewhat more brittle plastic. For this reason, the selection of the proper material for forming the sabot is of importance.

In use, the projectile C is inserted into the sabot A until the periphery of the rear end 15 of the projectile engages the marginal edges of the cavity formed by the surface 14, and the sabot is mounted in the cartridge B in the conventional way. When the cartridge B is placed in a gun and the gun is fired, the force of the explosion causes the assembled sabot and projectile to leave the rifle barrel, the sabot rotating in the same manner as the conventional projectile, and causing a corresponding rotation of the projectile C.

The force of the exploding gases acts against the closed end wall 11 of the sabot, tending to collapse the pocket or cavity between the end of the sabot and the end of the projectile. This action actually cracks the wall of the sabot longitudinally, as indicated in FIGURE of the drawings. FIGURE 5 was drawn from a sabot which had actually been fired in a rifle and the parts reassembled. During the travel of the sabot and the cartridge through the rifle barrel, the two parts remain assembled. However, as soon as the projectile leaves the muzzle of the rifle, the centrifugal force acting upon the sabot, and the wind resistance caused by the front of the sabot, acts to strip the sabot from the projectile, permitting the projectile to continue on its course at high velocity.

Slight variations in the construction may be made. It will be noted that while the structure of FIGURES 3 and 4 is virtually identical, the sabot of FIGURE 4 is provided with a rear end portion 16 of slightly decreased diameter. In view of the fact that the structures are otherwise identical, the same identifying numerals have been used.

The sabot D which is illustrated in FIGURE 6 of the drawings is essentially the same as the sabot A, and differs only in small details. The sabot D includes a cylindrical wall 20 having a closed end 21, the inner surface of which is generally conical in shape as indicated at 22. The sabot D differs from the sabot A in that the rear surface 23 of the closed end 21 is also generally cone shaped, the

4 surface of the cone being at an angle of perhaps 10 degrees from a plane normal to the axis of the sabot.

The angle of the conical surface 14 may vary to some extent, the angle between opposite sides of this surface on a plane including the axis of the sabot is perhaps 118 degrees. In some instances, this angle has been increased to as much as approximately degrees, the angle being measured between the broken lines 24 and 25 in FIGURE 3 of the drawings. Actually little difference in operation resulted from the increased angle, which decreased the size of the cavity.

In accordance with the patent statutes, I have described the principles of construction and operation of my improvement in sabots, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A sabot for use with a projectile, the sabot comprising a one piece sleeve of plastic material having an imperforate closed end, means forming a part of said closed end limiting the insertion of the projectile into the sleeve, said closed end including an internal cavity between the end of the fully inserted projectile and said closed end.

2. The structure of claim 1 and in which said internal cavity is substantially conical.

3. In a projectile for firing from a rifled barrel, a bullet having a maximum transverse dimension less than the bore of the barrel, and a sabot having a generally cylindrical outer surface of a diameter substantially equal to that of the bore of the barrel, said sabot including a sleeve portion encircling an end of said bullet and including an imperforate closed end overlying said end of said bullet, said closed end including an axial cavity between said bullet end and said closed end, said cavity being of suflicient size to permit inward flexing of the closed sabot end to at least partially close said cavity when said closed end is subjected to explosive pressure, and said sabot being of a material sufficiently fracturable to split the sleeve longitudinally when said closed end is flexed inwardly.

4. The structure of claim 3 and in which said cavity is substantially conical.

References Cited in the file of this patent UNITED STATES PATENTS 2,382,152 Iakobsson Aug. 14, 1945 2,638,051 Critchfield May 12, 1953 2,811,901 Barr Nov. 5, 1957 2,820,412 Beeuwkes et al. Jan. 21, 1958 2,983,224 Prosen et al. May 9, 1961 FOREIGN PATENTS 13,747 France June 13, 1855 

1. A SABOT FOR USE WITH A PROJECTILE, THE SABOT COMPRISING A ONE PIECE SLEEVE OF PLASTIC MATERIAL HAVING AN IMPERFORATE CLOSED END, MEANS FORMING A PART OF SAID CLOSED END LIMITING THE INSERTION OF THE PROJECTILE INTO THE SLEEVE, SAID CLOSED END INCLUDING AN INTERNAL CAVITY BETWEEN THE END OF THE FULLY INSERTED PROJECTILE AND SAID CLOSED END. 